The present invention is directed to rotary regenerative heat exchange apparatus that comprises a cylindrical mass of heat exchange material carried by a rotor around a central rotor post. The rotor is rotated about its axis slowly to alternately subject opposite sides of the rotor to streams of a heating fluid and a fluid to be heated.
When opposite sides of the rotor are subjected to extremes of temperature, the rotor is subjected to differential expansion that causes the rotor to deform and thereby alter the sealing relationship being maintained between the rotor and surrounding housing structure.
Since hot gases are usually ducted to the rotor from above and cool gases from below, the top of the rotor expands more than does the bottom of the rotor to assume the shape of a shallow inverted bowl conveniently called rotor "turndown".
Rotor turndown produces an excessive amount of leakage at the upper or hot end of the rotor. Consequently, various arrangements have been developed to provide sealing arrangements that permit rotor turndown while they provide a satisfactory deterrent to the leakage of the several fluids. The art is replete with examples of apparatus developed to contain fluids in heat exchangers subject to thermal deformation. U.S. Pat. Nos. 3,246,687 and 3,786,868 suggest moving a sector plate in accordance with rotor turndown, while U.S. Pat. Nos. 3,088,518 and 3,095,036 suggest moving a sealing means to fill an opening provided by the rotor turndown.
Thus it is common to provide variable sealing arrangements at the ends of the rotor to preclude the cross-flow of fluids being directed therethrough. A new approach to the sealing problem is advanced by U.S. Pat. No. 4,124,063 in which a sector plate at the end of the rotor is deformed into a curvilinear shape to correspond to rotor turndown on the adjacent face of the rotor.